1.1. Technical Field
The present invention relates to an initiation system for anionic polymerization of (meth)acrylic monomers and, possibly, ethylenically unsaturated monomers that can be copolymerized with these (meth)acrylic monomers to obtain homopolymers, block or random copolymers and star copolymers comprising arms formed of at least one (meth)acrylic sequence bonded to a core or node formed of a multifunctional compound (for example, a deactivating agent or a monomer lead to a polymer, whether or not cross-linked).
Anionic polymerization of (meth)acrylic monomers is difficult to control as a result of secondary reactions between the monomer and the initiator and/or the ends of growing anionic chains or due to termination and chain transfer reactions.
However, anionic polymerization is of interest in the sense that if it is conducted carefully under controlled conditions, polymers with a well-defined structure result.
1.2. Description of Related Art
Research has been undertaken for better control of (meth)acrylic monomer polymerization and to thus avoid secondary reactions.
Thus, in European Patent Application EP-A-524054, the anionic polymerization of (meth)acrylic polymers in the presence of an initiation system comprising a monofunctional or difunctional initiator and a ligand formed by an alkoxy alcoholate of an alkaline metal is described. With this process, polymerization is well controlled, especially at low temperatures.
An initiation system permitting well-controlled anionic polymerization, which can be used under conditions easy to create in industry and is less costly and, particularly, usable at temperatures closer to ambient temperature, is still being sought.